It is not free. As I understand it, we are recursively walking the
namespace tree with every ls to get this.
This is not a scalable design. Even posix doesn't do this!
This is a performance problem that will only get worse. I suggest
removing this performance mistake and documenting the existence of
dfs -du, which is a rather familiar solution to most users.
On Nov 15, 2006, at 12:19 PM, Yoram Arnon wrote:
I opt for displaying the size in bytes for now, since it's
computed anyway,
is readily available for free, and improves the UI.
If/when we fix HADOOP-713 we can replace the computation of size
with a
better value for #files.
Let's not prevent an improvement just because it might change in
the future.
Yoram
-----Original Message-----
From: Eric Baldeschwieler [mailto:[EMAIL PROTECTED]
Sent: Tuesday, November 14, 2006 7:10 PM
To: hadoop-dev@lucene.apache.org
Subject: Re: [jira] Created: (HADOOP-713) dfs list operation
is too expensive
So let's display nothing for now and revisit this once we have a
cleaner CRC story.
On Nov 14, 2006, at 10:55 AM, Hairong Kuang wrote:
Setting the size of a directory to be the # of files is a good
idea. But the
problem is that dfs name node has no idea of checksum
files. So the
number
of files include that of checksum files. But what's displayed at
the client
side has filtered out the checksum files. So the # of files does
not match
what's really displayed at the client side.
Hairong
-----Original Message-----
From: Arkady Borkovsky [mailto:[EMAIL PROTECTED]
Sent: Monday, November 13, 2006 5:07 PM
To: hadoop-dev@lucene.apache.org
Subject: Re: [jira] Created: (HADOOP-713) dfs list operation is too
expensive
When listing a directory, for directory entries it may be more
useful to
display the number of files in a directory, rather than the number
of bytes
used by all the files in the directory and its subdirectories.
This a subjective opinion -- comments?
(Currently, the value displayed subdirectory is "0")
On Nov 13, 2006, at 3:25 PM, Hairong Kuang (JIRA) wrote:
dfs list operation is too expensive
-----------------------------------
Key: HADOOP-713
URL:
http://issues.apache.org/jira/browse/HADOOP-713
Project: Hadoop
Issue Type: Improvement
Components: dfs
Affects Versions: 0.8.0
Reporter: Hairong Kuang
A list request to dfs returns an array of DFSFileInfo. A
DFSFileInfo
of a directory contains a field called contentsLen, indicating its
size which gets computed at the namenode side by resursively going
through its subdirs. At the same time, the whole dfs directory
tree is
locked.
The list operation is used a lot by DFSClient for listing a
directory,
getting a file's size and # of replicas, and getting the
size of dfs.
Only the last operation needs the field contentsLen to be computed.
To reduce its cost, we can add a flag to the list request.
ContentsLen
is computed If the flag is set. By default, the flag is false.
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